I can’t answer your question on whether it’s safe to use the plants medicinally within the year, but there are other options to assist in tooting besides just the commercially made rooting hormone. My dad is currently havign a blast propagating all kinds of cuttings from our blackberries and wild grapes, and he has been using the commercially made hormone. But yesterday, he came across a stand of willow trees and is going to be making some willow tea to use as a rooting aid on his next round of cuttings. So depending on the reasons for not using the plant in the first year (whether it’s waiting for potentially harmful compounds to dissipate or whether it’s just letting the plant fully establish) alternative whole plant hormone options may help you out.